Simple electronics question, please help...

[therafiman]

ok this may sound like a bit of a stupid question, but bear in mind it's been years since I messed around with any electronics so I only vaguely remember how to use a multimeter and the manual with it just says "put it on the appropriate setting".

I left my car sitting for a month or two, and the battery completely drained. So i've now recharged it, the car starts, but I want to make sure there isn't any electrical short anywhere that'll drain it again tonight, or i'll have to wait another few days for the recharge. My multimeter shows over 12v across it so thats ok, and it drops then goes up to just over 13 when the car's running, so i guess the alternator's ok too.

I then tried the ammeter-in-line-with-the-battery-cable thing i'd read about in older posts i'd searched through, and that's when I reached my first problem (and stupid question) - what setting should I put the ammeter on? I guessed either 20mA or 200mA, but i'm not sure (i can't remember what the reading represents or why the decimal point moves on other settings). Anyway, then theres problem no.2 - it didn't work. Basically, I took off the + cable, touched the red probe on it, and the black probe on the + battery connector. No reading. So I swapped the probes, still nothing. Tried the same with the negative cable, same result. And none of the car's electrics work when I'm doing this, so I can see why it wouldn't show a reading. But surely they're meant to work with the multimeter connected? Any help with this would b greatly appreciated because its confusing the hell out of me and I don't even know if i'm doing it right.

One last question - is it normal for a battery to drain this quick (its a stock carbed model so no amps/ecu to drain the power, only the clock and alarm/immobiliser) or is it a short like I think? This battery was bought last year, only used for a few months before it drained, and my last battery drained the same way, which makes me suspicious.

btw 4 any1 whos bored enuf 2 wana know, after only a year of owning this 3g that was meant 2 b my project car, some cunningly hidden rust has spread and eaten away at the arches and made a hole in the sill under the back door, so the car failed its MOT (yearly uk inspection), and after buying a mig welder the only thing i learnt was that welding is hard, so i've decided to get rid of the car. Yup, its the death of another 3g :violin: and i barely even got a chance 2 enjoy it. now im moving house and want 2 c the car go rather than moving it with me, so I need this problem fixed as quick as possible. So...help!!

p.s. if any1s from the uk and wants a very cheap (maybe even free) 3g or any parts, u kno who 2 ask ;)

[Kabuki]

An unused car will drain the battery in a month, even with the electrical system in perfect condition. I wouldn't worry about it. Just drive it around a little more.

[cardoc33]

ok this may sound like a bit of a stupid question, but bear in mind it's been years since I messed around with any electronics so I only vaguely remember how to use a multimeter and the manual with it just says "put it on the appropriate setting".

I left my car sitting for a month or two, and the battery completely drained. So i've now recharged it, the car starts, but I want to make sure there isn't any electrical short anywhere that'll drain it again tonight, or i'll have to wait another few days for the recharge. My multimeter shows over 12v across it so thats ok, and it drops then goes up to just over 13 when the car's running, so i guess the alternator's ok too.

I then tried the ammeter-in-line-with-the-battery-cable thing i'd read about in older posts i'd searched through, and that's when I reached my first problem (and stupid question) - what setting should I put the ammeter on? I guessed either 20mA or 200mA, but i'm not sure (i can't remember what the reading represents or why the decimal point moves on other settings). Anyway, then theres problem no.2 - it didn't work. Basically, I took off the + cable, touched the red probe on it, and the black probe on the + battery connector. No reading. So I swapped the probes, still nothing. Tried the same with the negative cable, same result. And none of the car's electrics work when I'm doing this, so I can see why it wouldn't show a reading. But surely they're meant to work with the multimeter connected? Any help with this would b greatly appreciated because its confusing the hell out of me and I don't even know if i'm doing it right.

One last question - is it normal for a battery to drain this quick (its a stock carbed model so no amps/ecu to drain the power, only the clock and alarm/immobiliser) or is it a short like I think? This battery was bought last year, only used for a few months before it drained, and my last battery drained the same way, which makes me suspicious.

btw 4 any1 whos bored enuf 2 wana know, after only a year of owning this 3g that was meant 2 b my project car, some cunningly hidden rust has spread and eaten away at the arches and made a hole in the sill under the back door, so the car failed its MOT (yearly uk inspection), and after buying a mig welder the only thing i learnt was that welding is hard, so i've decided to get rid of the car. Yup, its the death of another 3g :violin: and i barely even got a chance 2 enjoy it. now im moving house and want 2 c the car go rather than moving it with me, so I need this problem fixed as quick as possible. So...help!!

p.s. if any1s from the uk and wants a very cheap (maybe even free) 3g or any parts, u kno who 2 ask ;)


The alarm and clock may drain a battery over time. don't worry about it.
When you connected the MM across the cable and battery post, you were checking for a draw on the battery. the electrics wont work because the MM is not a straight thru connection, you actually put a load on the system and measure any flow. Since you didn't get a reading, either you have no draw(good), or you didn't have the MM set correctly(couldn't read the draw, the clock and alarm have only a few amps load,not enough to kill it overnight,no problem if you drive it every day). Make sure it's on the right setting, try changing it. Experiment.
Kabuki is right, just drive it, you'll be fine.

[therafiman]

Excellent, just the answers i was lookin 4 :) don't think i'll b drivin it any more, but i'll start it up for a few mins every morning until i get rid of it just 2 make sure it'll keep running.

Just out of interest tho, I watched my dad do the multimeter thing a while back, and when he opened the car door the interior light made the current reading go up. But in this case, no electrics = no readings no matter what I do. Tried all the ammeter settings. Which is y i feel i may b doin something wrong, seems like a slightly pointless test if nothing changes the reading. I guess it's not a problem for me now, but if anyone wants 2 explain further for future reference feel free.

Thanks 4 the quick replies :thumbup: